CMT1X phenotypes represent loss of GJB1 gene function.

Area of Science:

• Neurology
• Genetics
• Molecular Biology

Background:

• Charcot-Marie-Tooth type 1X (CMT1X) arises from over 260 mutations in the GJB1 gene, encoding connexin 32 (Cx32).
• The natural progression and mutation-specific severity of CMT1X are not well understood.
• The role of gain-of-function mechanisms in CMT1X pathogenesis remains unclear.

Purpose of the Study:

• To explore genotype-phenotype correlations in CMT1X.
• To characterize the natural history of CMT1X in male patients.

Main Methods:

• Evaluated 73 male patients with CMT1X, each harboring one of 28 distinct GJB1 mutations.
• Quantitatively assessed disability using the CMT Neuropathy Score (CMTNS), CMT Symptom Score (CMTSS), and CMT Examination Score (CMTES).
• Utilized neurophysiological assessments, including motor unit number estimates.

Main Results:

• Patient disability progressively increased with age.
• Disability levels were comparable to those seen with GJB1 deletions.
• A significant correlation was observed between disability and the loss of motor units.

Conclusions:

• The findings indicate that most GJB1 mutations lead to neuropathy through a loss of normal connexin 32 function.
• This loss-of-function mechanism suggests potential therapeutic benefits from gene replacement strategies for male CMT1X patients.